GABAA receptors are the target of clinically used benzodiazepines, which modulate multiple GABAA receptor subtypes non-selectively. While some progress has been made in identifying differential functions of GABAA receptor subtypes based on loss of function approaches which opens up the possibility to design novel treatments for CNS diseases such as anxiety disorders and depression, until now truly subtype-specific compounds are not available, thus limiting the information that is available on the function of individual GABAA receptor subtypes. Here we propose to use a novel combined genetic and pharmacological approach to create a model system (triple point-mutated mice + the non-selective drug diazepam) in which diazepam is a true ?1-specific, ?2-specific, ?3-specific, or ?5-specific full agonist, respectively, enabling the highly selective modulation of the activity of specific GABAA receptor subtypes in order to define the physiological and pharmacological functions of these receptor subtypes, in particular in the regulation of anxiety- and depression-related behaviors. PUBLIC HEALTH RELEVANCE: GABAA receptors are the target structures of clinically used benzodiazepines; however, we have only an incomplete knowledge of the function of individual GABAA receptors subtypes, in large part due to the lack of fully subtype-specific compounds. We are proposing a novel genetic and pharmacological approach to assess the anxiety-reducing and antidepressant-like properties of specific GABAA receptor subtypes. The proposed experiments are expected to clarify the potential role of specific GABAA receptor subtypes as targets for the development of novel antidepressant drugs.